Weather Wise

I HAVE just met a formula that explains Europe's weather. Going by the name of Gorczynski's Continentality Index, it says:

K = 1.7(A/sinu) - 20.4

where A is the annual temperature range in degrees Celsius, and u is the latitude angle of the location under consideration.

The idea of the formula is to obtain a precise measure of the difference in climate between places near the sea and those in the middle of a land mass. In general, places with a maritime climate will have a lower range of temperature (A) than landlocked locations. With the oceans releasing their stored heat at a slower rate than the land, they provide a sort of thermal lagging for anywhere near the coast. Britain, for example, has a generally moderate climate because the sea is colder than the land in summer and warmer than the land in winter, thus cooling us down when it's hot, and warming us when it's cold.

So the value of K in the formula will be higher in places far from the sea where A takes a larger value. The "sin u" term simply enables fair comparisons to be made between places on different latitudes.

When all the values of K have been worked out, they are then scaled to produce a range from zero at the most oceanic sites to 100 at extreme continental locations. Values of the scaled figures in Europe include 10 for London, 21 for Berlin and 42 for Moscow - which is a fair reflection of the bitter Russian winters.

Britain is parked in a particularly fine spot because it benefits also from the North Atlantic Drift (the extension of the Gulf Stream) by which the prevailing south-westerly winds bring warm water from Florida slowly in our direction (the water takes almost a year to complete the journey). So while our maritime climate brings us lower extremes of temperature, the overall temperatures are higher than might be expected anyway.

Even taking all this into account, it is striking just how different climates can be at places at the same latitude. The north of Scotland, for example, enjoys January temperatures some 20C higher than the world average at the same latitude, while temperatures at certain locations in the south-east of Siberia - again at the same latitude - may be 45C lower than average.

It's not just how much sunshine a place receives - it's how well the oceans store and spread that energy that determines the climate.